As one of the world's most earthquake-prone nations, Japan has had considerable experience of tsunamis.

The very word is Japanese, and probably the most famous Japanese painting, by 18th Century artist Hokusai, depicts a tsunami passing by Mount Fuji.

So seriously does Japan take the tsunami threat that one university even has a specialist engineering faculty to study the natural effect.

There is also a Tsunami Warning Service, established in 1952, and run by the Japan Meteorological Society (JMA).

Six regional centres connected up to 300 sensors located across Japan's islands, including around 80 water-borne sensors, monitor seismic activity round the clock.

If an earthquake looks as if it has the potential to trigger a tsunami, the JMA issues an alert within three minutes of it being identified.

If some of these countries like Sri Lanka had a system like ours perhaps we could have saved lots of lives

Makoto Hikida, Kobe quake survivor

The alerts are broadcast on all radio and TV channels, and if necessary an evacuation warning is also given.

The JMA aims to give people in the path of the wave at least 10 minutes' warning to evacuate the area.

Local authorities, central government and disaster relief organisations also get warnings via special channels so they can respond to a disaster swiftly.

So sophisticated is the JMA's network that it can predict the height, speed, destination and arrival time of any tsunami destined for Japanese shores.

System cost

Underpinning this cutting-edge warning system are strict new building laws to protect against tsunamis and quakes, and good disaster planning that have so far kept Japanese casualties from such natural disasters low for such a vulnerable nation.

When a 30-metre-high tsunami swamped part of the northern island of Hokkaido in 1993 there were only 239 fatalities from the tsunami and quake.

Residents could thank tsunami walls, strong buildings and disaster awareness for their good fortune. While the JMA got a warning out within five minutes, the tremor was so close to shore that by the time the warning was issued the first wave had struck.

But Makoto Hikida, who survived the 1995 Kobe earthquake, told the BBC News website: "We have great faith in the JMA, they do a good job in saving people's lives, if some of these countries like Sri Lanka had a system like ours perhaps we could have saved lots of lives."

Japan's system is being upgraded constantly. In 1999, a new tsunami-forecasting model was introduced. But the system comes with a price-tag - around US$20m a year.

Not much for wealthy Japan, but a price that some poorer countries might balk at.

Time to warn

However, as Hokkaido's residents know, it is not just an early-warning system that saves lives.

Shizuoka prefecture, on Japan's tsunami-prone east coast, has 258 tsunami and quake-resistant shelters along its shoreline. Other coastal towns have built floodgates to prevent water from tsunamis heading inland through rivers and wreaking more havoc.

Tsunami walls also ring other parts of the coast to prevent damage.

But these walls are rarely more than a few metres high, and would not have fully protected against the tsunami in the Indian Ocean in December.

So even with all these precautions and warning systems, Japan still remains at risk.

According to government estimates, if the worst-case scenario of three simultaneous strong quakes across Japan was to occur, up to 12,700 people could be killed in the resulting tsunami.

With some underwater quakes in Japan occurring just a few kilometres offshore, it could take only five minutes for tsunamis to hit land. That would make even Japan's cutting-edge system effectively useless, without further advances.